sorry was miles away and rushing.
i've rooted my nexus 7 then tried the usb disable power app,worked twice out of 20 attempts.
i've just today spliced my usb cable and tried disconnecting the black and red cables in different orders,it'll stop charging but as soon as i disconnect one of those 2 wires the app loses connection.
at this moment in time i think i'm just going to fly with a power bank on the back of my nexus and charge the rc via the top left side connection whilst flying.